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HVAC Pros vs. Plumbers

Hello!

I am new to the forum so please be gentle

We are in the process of buying a home that does not have central AC (yet). It's about 6000SF located in the Northeast.

One of the issues I've had in the past was with a plumber that "installed AC systems". To my chagrin, this has resulted in mediocre performance of my AC system. At the end of the day, it takes forever to cool the house down because the "professional" didn't size my units properly (confirmed by others who've serviced my equipment).

I've also been told there's a world of difference between HVAC pros and plumbers that install AC units.

I'm looking for some help if finding people who are truly great at HVAC and can install and stand behind a 6000SF retrofit where the installation will be properly sized and calculated for the environment. Are there certain questions I should ask? Are there certain "red flag responses"? I'm all ears and thank you for taking the time to read this.

We are in the process of buying a home that does not have central AC (yet). It's about 6000SF located in the Northeast.

One of the issues I've had in the past was with a plumber that "installed AC systems". To my chagrin, this has resulted in mediocre performance of my AC system. At the end of the day, it takes forever to cool the house down because the "professional" didn't size my units properly (confirmed by others who've serviced my equipment).

I've also been told there's a world of difference between HVAC pros and plumbers that install AC units.

I'm looking for some help if finding people who are truly great at HVAC and can install and stand behind a 6000SF retrofit where the installation will be properly sized and calculated for the environment. Are there certain questions I should ask? Are there certain "red flag responses"? I'm all ears and thank you for taking the time to read this.

Find an HVAC company that will do a Manual J and D calculation. Post your location and check the contractor locator in the index on this site and perhaps someone will be in your area.

Original A/C equipment may not be performing well &, may not be undersized

We need to know a lot more about your situation.
In the NE, what large city do you live near?

Your A/C may not be undersized but rather it may not be performing near up to par.

Simple easy anyone can do ways to check the performance of your central air conditioner so, if needed; you can call an Energy Efficiency HVAC Technician. Want to find out...?

If U want us to run a ballpark analysis of how your system is performing in respect to its 'Nominal Rated Btuh' we need at least the following information & numbers:

Performance Data Collection – Best Time to collect data is late afternoon around 4:30 pm, when attic is HOT; also when outdoor temps are around 85; 95; 105F or, anywhere in between.
*All U need is a good thermometer (digital reading in tenths preferable) & and indoor Humidity Gauge

If U can find a turn in the small liquid line insulate the temperature-probe; get its temperature for the subcooling analysis:
Small liquid line temperature ____F

To measure return air the wet bulb temp, wrap a small/thin, wet (not dripping) piece of cloth around the probe and put it into the Return Air grille & then close to the closest Supply Air diffuser near the air handler (need air movement). Wait until the temperature stabilizes - may take a little while.

One of the issues I've had in the past was with a plumber that "installed AC systems". To my chagrin, this has resulted in mediocre performance of my AC system. At the end of the day, it takes forever to cool the house down because the "professional" didn't size my units properly (confirmed by others who've serviced my equipment).

I've also been told there's a world of difference between HVAC pros and plumbers that install AC units.

.

Lets not lump all the plumbers into your s list.
While I'm a licensed HVAC contractor- I'm also licensed separately in plumbing, fire sprinklers, landscaping, swimming pools, medical gasses, electrical, as well as a general contractor.
There's plenty of hack HVAC contractors out there who don't perform Man J & D load calcs, so don't think your issues are exclusive to your guy. You could have easily got screwed by an a/c guy as well. Just read these forums for awhile & you'll see.

Lets not lump all the plumbers into your s list.
While I'm a licensed HVAC contractor- I'm also licensed separately in plumbing, fire sprinklers, landscaping, swimming pools, medical gasses, electrical, as well as a general contractor.
There's plenty of hack HVAC contractors out there who don't perform Man J & D load calcs, so don't think your issues are exclusive to your guy. You could have easily got screwed by an a/c guy as well. Just read these forums for awhile & you'll see.

As hard as it is to find a company that is proficient at one discipline the chances are even rarer to find one that is diversified. There are a few but quite limmited

The location would be closest to Manchester, NH. Would love recommendations of those who run Manual J and D calcs as a pre-req that are in my region.

The 2.5% summer design at Manchester is 88-F dry bulb & 71-F wet bulb or about 43% relative humidity. Doubt you'd have a lot of hot days up there...

We are in the process of buying a home that does not have central AC (yet). It's about 6000SF located in the Northeast.

One of the issues I've had in the past was with a plumber that "installed AC systems". To my chagrin, this has resulted in mediocre performance of my AC system. At the end of the day, it takes forever to cool the house down because the "professional" didn't size my units properly (confirmed by others who've serviced my equipment)

Your present poor performing system is what you could collect the temperatures on for analysis...
----
IMO, for more efficient performance you'll need at least two units for the future 6,000-sf home in NH.

Are there two furnaces? Duct systems for heating are seldom sized large enough to work well for cooling.

I'd definitely have a "Home Energy Efficiency Audit," performed on that home, that doesn't yet have central air; so work could be done to lower the heat-gain & heat-loss.

Then after that work is done have the load calcs done.
Yes, a Manual D for designing the duct system is also definitely called for.

Thanks udarrell....the problem in the Northeast is worse that you might think. Not only do we have more hot days that you give us credit for, we also have VERY humid days such as the last 4 or 5 days just as a small example. I'm looking for AC to condition the air...not just cool it. Sticky 70 degree days are worse than dry 85 degree days imo.

Is it standard for HVAC pros to do "Home Energy Efficiency Audits" done? If not, who does them? Approx cost?

Thanks udarrell....the problem in the Northeast is worse that you might think. Not only do we have more hot days than you give us credit for, we also have VERY humid days such as the last 4 or 5 days just as a small example. I'm looking for an AC to condition the air...not just cool it. Sticky 70 degree days are worse than dry 85 degree days imo.

Is it standard for HVAC pros to do "Home Energy Efficiency Audits" done? If not, who does them? Approx cost? Thanks!

It will become more standard in the future as they gear-up to the whole home concept along with "Testing the Actual Delivered Performance" of the equipment.

Some utility companies will do them at no cost or for a lesser fee than other sources; so be sure to ask both the electrical & heating fuel companies.

For mild high humidity days IMO, U need a slightly undersized A/C with a temperature differential SWING digital programmable thermostat. That allows U in milder weather to get longer-runtime cycles for increased dehumidification.

I wouldn't go higher than a 14-SEER & I'd operate the indoor blower at 350-CFM per/ton of cooling, or even slightly less than 350-CFM. You want the evaporator coil operating at well under the dew point temperature of the air passing through it.

The indoor coil must have a TXV metering device for safe operation at low CFM blower settings.

Thanks udarrell...do these recommendations also apply when there's 20 people in the house? I've been told that each adult is about 800 BTU's worth of cooling and that a properly designed system will factor that in...as well as kitchen stove/oven allowances, etc...

Are those CFM's residential standard or are they calculated per house with manual D/J?

Typically in residential you don't design for maximum occupancy sine it's no ta high probablility that max occupancy will coincide with the hotest weather. You normally design for normal occupancy at design conditions and some appliance loads are factored in. Do you factor in the possibility that you might entertain a large number of guests on a very hot day and cook all afternoon leading up to it? You may want ot factor that in. It's a good reason to have either zoning or vairable capacity equipment on larger homes where you may entertain. For example, for that same reason you may want the downstairs AC to be designed for low ambient cooling if you don't plan on operning windows to cool the space in cooler weather. In some situations, noise, privacy, dust, etc. mean you prefer not to open windows in many situations.

However, if you entertain frequently with a large number of guests, you amy then want ot treat that space or zone more like a light commercial space and consider a package unit with an economizer and ventilation based on CO2 levels.

Finally, once your at or around may 5000+sqft and have larger occupancy requirements, for best comfort, you may want to start looking at a chilled water system for the best climate control over a wide range of heat loads with hot water reheat for dehumidification or large capacity whole house dehumidifiers.